Pdc problem with a difference

[bakester69]

Hi all,
Hoping someone can help as it is starting to annoy me now! All i seem to be doing with the x is throwing money at it. I have read all about different parking sensor faults etc but none of them seem to relate to mine. Basically....
When i put it in reverse, i get a long beep then the pdc light flashes. From what i have read, this means a duff sensor, but the problem is that none of the sensors are clicking to help me find the bad one :-(
When i have been playing around to try and find the problem, i have found that when the blue plug is removed from the pdc module, all of the rear sensors are clicking but still dont work.
Hopefully someone can shed some light on the subject as it is really starting to p**s me off. I asked my local bmw btw and they wanted £75 to scan the errors and couldnt guarentee they would be able to diagnose for that price.

Any help will be greatly appreciated.